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Ab initio studies of strained wurtzite GaN surfaces.

Abstract

In GaN and other group III nitrides the considerable lattice mismatch with the
substrates normally employed during growth, such as sapphire, 6H-SiC and
ZnO, can lead to the presence of strain which may affect the surface properties.
Here we have studied the effect of biaxial strain on the structure, electronic
configuration and formation energy of various GaN(0001) and (000¯1) 1 × 1
surfaces. In particular, we consider the Ga and N tetrahedral (T4), hexagonal
(H3) and asymmetric top (atop) configurations. The ab initio total energy
calculation studies presented here employ the density functional formalism
using a pseudopotential plane-wave basis set approach in order to obtain
the minimum energy configurations of the unstrained and biaxially strained
structures. We show in bulk GaN a good linearity between the biaxial strain
imposed and the calculated structural cell parameters. The calculated formation
energies of the GaN surfaces show that the most stable configuration for the
different reconstructions is not influenced by the biaxial strain.